Use debug wisely

When troubleshooting a router problem, sometimes "show" commands don't give you all the information you need. For more detailed information, Cisco has a series of "debug" commands which you can see by typing "debug ?".

Unfortunately, "debug" commands carry some risks when used on a production network, since they take up a lot of resources, and since routers give them priority over other tasks.

Therefore, it's very important to remember to turn debugging off when you're done, such as with the "no debug" command. Similarly, if the network is mysteriously slow, you can type "show debug" to check if a debugging command left on might be the reason.

Also, avoid the temptation to issue multiple debug commands at once, or to issue the "debug all" command (which risks overwhelming the server). Because debugging has an impact on router speed, one kind of debug command can influence the results in another kind, making it more difficult to get to the root of the problem. Hence, issuing the commands at different times is more effective.

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